polar coordinates : Java Glossary

Many geometric shapes, such as circles, spirals and polygons are easier to describe
in polar coordinates, with an angle and radius instead of x,y. You have a central
point and you measure the angle in radians counter clockwise from due east. You
measure the radius as the distance from the centre.

If your angles are in degrees, to see how to convert them to radians, see the
radians entry. To convert to drawing
coordinates you must round to integers and invert the sign of y, since y grows down
in Java rather than up as in mathematics.